1. Field of the Invention
The present invention relates generally to a data transmission apparatus for controlling a flow of packets in a data transmission path and a method of operating the same.
2. Description of the Background Art
Some of data processors such as data flow type information processors employ data transmission paths using self-oscillation circuits. An arbitration portion is provided, for example, when transmitting packets flowing through two input side data transmission paths provided in parallel with each other to one output side data transmission path in the order of arrival or when in performing read and write with respect to the same memory in the order of arrival of the packets. The arbitration portion is supplied with signals indicative of an arrival of a packet and the portion applies a transmission acknowledging signal to the data transmission path which has first generated the signal. A word number counting portion is provided when a plurality of packets are to be collectively treated. The word counting portion performs arbitration such that a prescribed number of packets are successively transmitted.
FIG. 16 shows one example of a conventional data transmission apparatus.
In FIG. 16, data transmission paths 100 and 200 are provided in parallel to each other on the input side. The data transmission path 100 applies a transmission acknowledging signal AK100 to a data transmission path (not shown) at the preceding stage and receives a transmission signal C100 from that data transmission path. The data transmission path 100 also receives a transmission acknowledging signal AK301 from an arbitration portion 500 and applies a transmission signal C301 to a data transmission path 300 on the output side. Similarly, the data transmission path 200 applies a transmission acknowledging signal AK200 to a data transmission path (not shown) at the preceding stage and receives a transmission signal C200 from that data transmission path. The data transmission path 200 also receives a transmission acknowledging signal AK302 from the arbitration portion 500 and applies a transmission signal C302 to the data transmission path 300 on the output side. A word number counting portion 400 receives transmission acknowledging signals AK100 and AK200 from the data transmission paths 100 and 200, respectively and applies transmission acknowledging signals AK101 and AK201 to the arbitration portion 500. The arbitration portion 500 receives a transmission acknowledging signal AK300 from the data transmission path 300 on the output side.
The data transmission path 100 holds and outputs a received n-bit data DATA1 in response to the transmission signal C100 when the transmission acknowledging signal AK301 is at an acknowledged state. Similarly, when the transmission acknowledging signal AK302 is at an acknowledged state, the data transmission path 200 holds and outputs a received n-bit data DATA2 in response to the transmission signal C200.
The word number counting portion 400 counts the number of packets transmitted from the data transmission path 100 to the data transmission path 300 in response to the transmission acknowledging signal AK100 to output the transmission acknowledging signal AK101. The word number counting portion 400 also counts the number of packets transmitted from the data transmission path 200 to the data transmission path 300 in response to the transmission acknowledging signal AK200 to generate the transmission acknowledging signal AK201. The arbitration portion 500 causes one of the transmission acknowledging signals AK301 and AK302 to enter an acknowledged state and the other to enter an inhibited state. The arbitration portion 500 maintains the state of the transmission acknowledging signals AK301 and AK302 in response to the transmission acknowledging signals AK101 and AK201 until a prescribed number of packets are successively transmitted from one of the data transmission paths 100 and 200 to the data transmission path 300.
A prescribed number of packets are successively transmitted from one of the data transmission paths 100 and 200 to the data transmission path 300 in the order of arrival in this way.
For the above-described conventional data transmission apparatus, the number of packets to be successively transmitted is predetermined depending on an arrangement of the word number counting portion 400, so that the number of packets to be collectively treated is constant at any time. Therefore, when packets to be collectively treated change in number, it is necessary to fix the number of packets at a prescribed number by adding dummy packets or the like.